For five years, Clinton Maynard had used the same routine to top up the chemicals in his backyard pool without a problem.
Two weeks ago, the water had turned green and a pool shop calculated two kilograms of chlorine was needed to bring it back to a healthy sparkling blue.
Mr Maynard, the news content director for 2UE, said his wife, Cas, measured the stabilised chlorine granules into a bucket then went to put one of their children to bed at their home in Engadine.
He then put water into the bucket from the pool and started mixing it.
He was not prepared for what happened next.
''After about 30 seconds of mixing, it exploded,'' Mr Maynard said. ''It was a fairly big blast and then there were a series of other explosions afterwards, about five blasts.
''All the watery chlorine went on me - I was thrown to the ground. I was really lucky my neighbours were at home at the time. They dragged me out from behind the pool fence and straight away they put a hose on me. They ripped my clothes off and doused me with water. The fire brigade arrived and they put their hose on me as well.''
Mr Maynard was taken by ambulance to St George Hospital in a critical condition as paramedics in the ambulance continually flushed his eyes with water. His lungs were also affected by the chemical and he was placed in intensive care on oxygen with pneumonia-like symptoms.
Now out of hospital a week, Mr Maynard says he believes retailers of pool chemicals should give customers a verbal warning as well as relying on the small print of instructions printed on the packaging.
''We were told years ago to add the chemicals the way we have done it for years,'' he said.
''I am told you should add the chlorine to the water. We had the chlorine in the bucket first and then put the water in it. What's the difference? Well, the difference is it can cause a reaction and then an explosion.
''I think there needs to be some sort of obligation on the people who retail these chemicals to actually say, 'Make sure you do it this way. The risk if you do it the wrong way could be potentially fatal.'''
A spokeswoman for Fire and Rescue NSW said they had attended six incidents involving chlorine used for swimming pools since the start of summer.
Three cases required hospital treatment and three needed spills from leaking containers to be neutralised.
Senior firefighter Richard Neville, who is on the the Fire and Rescue hazardous materials advisory team, said the reaction of adding a small amount of water to a large amount of a chlorine pool compound could generate intense heat.
''The concentrated heat could lead to steam carrying chlorine compounds or corrosive gases being liberated. It is a complex mixture,'' he said.
Mr Neville said it was good practice not to allow any small amount of liquid to get into a large amount of pool chemicals.